Typings for "normalized" redux state shape

Question

Redux best practices recommend that your normalize your state shape

basically that means that the following:

const blogPosts = [
    {
        id : "post1",
        author : {username : "user1", name : "User 1"},
        body : "......",
        comments : [
            {
                id : "comment1",
                author : {username : "user2", name : "User 2"},
                comment : ".....",
            },
            {
                id : "comment2",
                author : {username : "user3", name : "User 3"},
                comment : ".....",
            }
        ]    
    },
    {
        id : "post2",
        author : {username : "user2", name : "User 2"},
        body : "......",
        comments : [
            {
                id : "comment3",
                author : {username : "user3", name : "User 3"},
                comment : ".....",
            },
            {
                id : "comment4",
                author : {username : "user1", name : "User 1"},
                comment : ".....",
            },
            {
                id : "comment5",
                author : {username : "user3", name : "User 3"},
                comment : ".....",
            }
        ]    
    }
    // and repeat many times
]

Should be stored like this:

{
    posts : {
        byId : {
            "post1" : {
                id : "post1",
                author : "user1",
                body : "......",
                comments : ["comment1", "comment2"]    
            },
            "post2" : {
                id : "post2",
                author : "user2",
                body : "......",
                comments : ["comment3", "comment4", "comment5"]    
            }
        }
        allIds : ["post1", "post2"]
    },
    comments : {
        byId : {
            "comment1" : {
                id : "comment1",
                author : "user2",
                comment : ".....",
            },
            "comment2" : {
                id : "comment2",
                author : "user3",
                comment : ".....",
            },
            "comment3" : {
                id : "comment3",
                author : "user3",
                comment : ".....",
            },
            "comment4" : {
                id : "comment4",
                author : "user1",
                comment : ".....",
            },
            "comment5" : {
                id : "comment5",
                author : "user3",
                comment : ".....",
            },
        },
        allIds : ["comment1", "comment2", "comment3", "commment4", "comment5"]
    },
    users : {
        byId : {
            "user1" : {
                username : "user1",
                name : "User 1",
            }
            "user2" : {
                username : "user2",
                name : "User 2",
            }
            "user3" : {
                username : "user3",
                name : "User 3",
            }
        },
        allIds : ["user1", "user2", "user3"]
    }
}

Since the Key is a unique Id, typescript wants each key to basically be a property (eg: comment1, comment2)...

So what is the best way to type the above data structure?

Answer 1

The keys are strings, so you can define your type as an object type, like this:

interface NormalizedObjects<T> {
  byId: { [id: string]: T };
  allIds: string[];
}

interface ReduxState {
  posts: NormalizedObjects<Post>;
  comments: NormalizedObjects<Comment>;
  users: NormalizedObjects<User>;
}